Conventional Ethernet cables employ eight wires, only four of which are used to carry communication signals. The other wires are available for other uses. One such use is to carry power from one Ethernet-connected device to another such device. This allows the device receiving the power to avoid the need to obtain power from a separate source.
Providing power over Ethernet cables can involve power detection and control circuitry in addition to the other circuitry for which the power is intended. It can be desirable to allow for communication between the power detection and control circuitry and other circuitry, for example, to allow the other circuitry to provide commands to, and receive status from, the power detection and control circuitry.
However, if power supplied is improperly received, or a surge in power occurs, the power detection and control circuitry can receive sufficient power to damage the power detection and control circuitry. Although the repair of such circuitry may involve replacement of a relatively-inexpensive module containing the power detection and control circuitry, the power that damages such circuitry can be transmitted to the other circuitry from which commands are received and to which commands are provided, damaging such other circuitry as well. What is needed is a system and method that can protect the power and control circuitry providing power over Ethernet cables from transmitting abnormal power to the other circuitry with which it is in communication.